USB (Universal Serial Bus) and Firewire, IEEE 1394, are standard digital interfaces for connecting devices to a personal computer. These interfaces are hot-pluggable, which means that devices can be plugged in and unplugged from the interface without rebooting the personal computer, and connected devices are automatically recognized by the personal computer, which is described as “Plug and Play”. One class of available USB or Firewire devices are storage devices like hard disks, memory sticks or other flash memory devices. USB and Firewire storage devices should always be unmounted before they are disconnected from the interface to avoid any data loss during a not finished operation. However, the USB and the Firewire interface have no mechanism to prevent users from disconnecting a storage device which is still mounted. In most user scenarios, the unmount action has to be triggered by the end user. Therefore, performing this unmount action should be as less cumbersome as possible.
An extension of “Plug and Play” is UPnP, “Universal Plug and Play”, which is defined by an International Standard, ISO/IEC 29341. UPnP defines control points which are devices using UPnP protocols to control UPnP devices and defines actions for rendering pictures, music and videos. Although a control point can manage multiple UPnP devices, all interactions occur in isolation between the control point and each UPnP device. The individual UPnP devices do not interact directly with each another. In particular residential gateways usually include a UPnP architecture to allow device-to-device networking with personal computers, networked home appliances, removable storage devices or other consumer electronics devices.
An audio and video extension of UPnP is UPnP AV (UPnP for Audio/Video), which allows a higher level of interoperability between UPnP devices. UPnP AV allows to deliver streaming media, for example real-time audio/video streams, for which it is critical to be delivered within a specific time, or the stream is interrupted. The current UPnP AV v2 specification is defined by the UPnP Forum, which is a group of companies and individuals across multiple industries that play a leading role in the authoring of specifications for UPnP devices and services.
UPnP AV defines three services: a media server for serving media content, a media renderer capable of playing one or more media formats, and a control point for controlling the media server and the media renderer. An environment with a UPnP AV media server 1, a control point 2 and a media renderer 3 is shown in FIG. 1, wherein the media server, the media renderer and the control point are separate devices according to a 3-Box model. The media server 1 may have for example a USB or Firewire digital interface, via which a removable storage device containing audio/video media can be connected to the media server 1. The control point 2 coordinates the operation of the media server 1 and the media renderer 3 to achieve an overall, synchronized end-user effect. The media server 1 and the media renderer 3 do not interact directly with each another, all of the coordination between the two devices is performed by the control point 2.
In FIG. 2 a situation is shown wherein the media server 1 is implemented in a residential gateway 13, to which two USB storage disks 11, 12 are attached. On a smartphone 14 an UPnP AV control point application has been installed, so that the smartphone 14 can operate as a control point 2 as described with regard to FIG. 1. The media renderer 3 is a flat-screen TV 15, which is capable of playing movies, music and pictures. The residential gateway 13 comprises a webserver 16 for providing Internet services, which webserver includes a webpage as a user interface to be used by a user for configuring the residential gateway 13. The user browses through the media file collection on the media server 1 by making use of the control point software of his smartphone 14.
The media files are organized in a hierarchy of file containers, which is similar to a file system organizing files in directories, which can be displayed in a display 17 of the smartphone 14. The file containers are arranged for example in a root container or root container of the smartphone 14, and for each media category “music”, “movies” and “pictures” advantageously a dedicated file container is provided. The user can navigate with the smartphone 14 through the media just like with a file system explorer. When the user selects a media file on the media server 1 to play, step A, a play action message is send from the smartphone 14 to the media server 1, step B. The media server 1 acts on the play message by streaming the selected media file towards the media renderer 3, step C.
Now, the user wants to disconnect one of the storage disks 11, 12. Before disconnecting a disk, the user has to unmount the disk in order to avoid file system corruption. However, the UPnP AV specification does not define an action for unmounting of disks. Therefore, manufacturers of media servers with support for external disks implement a proprietary solution for unmounting of external disks.
In FIG. 3, an unmount method available in many media servers, including residential gateways, is illustrated. The webserver 16 has a webpage 18, dedicated for unmounting of external storage devices. For unmounting one of the storage disks 11, 12, the user has to perform the following steps:                the user has to open a web browser on the controlling device, i.e. the smartphone 14 as the control point 2, step D,        the user has to surf to the web interface of the media server 1, step E, so he has to know the IP address of the media server 1,        the user usually needs to enter a login and/or a password to gain access to the web pages of the media server 1, step F,        the user should know on which web page: web page 18, the unmount buttons 19 are located, which may not be obvious for a novice user, and        The user has to surf to the webpage 18, step G, click on the web page 18, step H, so that the web page 18 opens on the display 17 of the smart phone 14, step I, and to click on one of the unmount buttons 19, step J.        
This method for unmounting a disk in an UPnP AV environment is therefore not user friendly. It is also noted that a web browser is not per definition available on a control point: instead of a smartphone, also any other possible control point device, for example a dedicated remote control unit without a web browser, may be used. The necessity to start another application and having to know technical details, like the IP address of the media server 1, are against the plug and play philosophy of the UPnP protocol. Since it is so cumbersome in an UPnP AV environment to unmount a disk with this method, it is not uncommon that many users will not use this method, and disconnect a disk without unmounting it. This will almost certainly lead to file system corruption in a percentage of cases, and it may even result in data loss. The user manual can describe that an external disk should always be unmounted before it will be disconnected, which is good as a countermeasure against legal claims, but it will not avoid that users disconnect mounted disks.
As a further remark, the current USB and Firewire specifications do not allow to use a hardware solution for the unmount problem. For instance, it is supposed that the residential gateway 13 has a hardware unmount button close to the USB and Firewire interfaces, and a status LED indicates when it is safe to disconnect the disk. Such a hardware implementation will only work when only one disk is connected to the interface of the residential gateway 13. But since USB and Firewire are bus interfaces, multiple disks can be connected to the interface by making use of a hub. Thus, when using a hub, selective unmounting is not possible with such a hardware implementation, because either all disks will be unmounted at once, or no disk will be unmounted at all.
External, respectively portable storage devices are also used with personal computers and laptops. Unmounting a storage device makes it inaccessible by the computer. In order for a storage device to be unmounted, it must first be mounted. Mounting takes place before a computer can use the respective storage device and is done automatically in accordance with the “Plug and Play” architecture. When a storage disk is mounted, it is active and the computer can access its contents. Since unmounting a disk prevents the computer from accessing it, there is no risk of the disk being disconnected in the middle of a data transfer. Therefore, before removing an external storage device, such as a USB flash drive or a USB hard disk, the storage device should be unmounted to avoid possible data corruption.
Several types of storage devices can be unmounted, including external hard drives, USB flash drives, iPods, flash memory cards, and disk images. In order to unmount a disk in the Microsoft Windows operating system, the following steps are necessary: opening “My Computer,” selecting the disk, and clicking the “Eject this disk” option in the left sidebar. In the Apple Mac OS X operating system, the following steps are necessary: selecting the disk on the desktop and either drag the disk to the trash, which changes to an Eject icon, or selecting “File→Eject” from the Finder's menu bar. Once a removable disk has been unmounted, it can safely be disconnected from the computer.
U.S. Pat. No. 7,234,014 describes a portable storage device including a body, an actuator and an indicator. When the storage device is coupled to a host device, an unmount operation can be performed by a user by depressing the actuator, which causes an interrupt message to be send to the host device for initiating shut-down of the portable storage device by removing it from a host device list of available storage media, and which depowers the portable storage device. After the unmount operation, the indicator then changes to signify that it is safe now to remove the portable storage device from the host device.
U.S. 2006/0200570 describes a method for mounting network file systems to a client arrangement via a peer-to-peer local area network, which uses a network file protocol being compatible with the client arrangement. A network file system can be unmounted by using the compatible network file protocol in response to a signal for disconnecting the client arrangement from the peer-to-peer local area network.